1. Technical Field
The present invention relates generally to miniature hearing aids, acoustic and otherwise, which are fitted deeply in the ear canal.
2. Description of the Prior Art
(1) Brief Description of the Ear Canal and Canal Hearing Aids
The external acoustic meatus (ear canal) is generally narrow and contoured as shown in the coronal view in FIG. 1. The ear canal 10 is an elongated cavity beginning at the canal aperture 17 and ending medially with the tympanic membrane 18 (eardrum). The cartilaginous region 11 is relatively flexible due to the underlying cartilaginous tissue. The medial (towards the tympanic membrane) part, a bony region 13 proximal to the tympanic membrane, is rigid due to the underlying bony tissue. The skin 14 in the bony region 13 is thin (relative to the skin 16 in the cartilaginous region) and is more sensitive to touch or pressure. There is a characteristic bend 15 that roughly occurs at the bony-cartilaginous junction 19 (referred to herein as the bony junction), which separates the cartilaginous 11 and the bony 13 regions. The magnitude of this bend varies among individuals. The cross section of the ear canal is generally oval (FIG. 2) having a long diameter (DL) and a short diameter (DS)
Hair 12 and debris 4 in the ear canal are primarily present in the cartilaginous region 11. Physiologic debris includes cerumen (earwax), sweat, exfoliated skin and hair, and oils produced by the various glands underneath the skin in the cartilaginous region. Non-physiologic debris consists primarily of environmental particles that enter the ear canal. Canal debris is naturally extruded to the outside of the ear by the process of lateral epithelial cell migration that begins on the eardrum and extends the length of the ear canal. There is no cerumen production or hair in the bony part of the ear canal. Laterally and external to the ear canal is the concha cavity 2 and the auricle 3, both also cartilaginous.
Conventional canal hearing aids are removed daily from the ear in order for the ear canal to “dry out” after being occluded by the hearing aid.
(2) Review of State-of-the-Art in Canal Hearing Aid Technology
Recent advances have led to the development of extended-wear canal hearing devices, which are operated continuously deep in the ear canal for several months before removal. These deep canal hearing devices are completely inconspicuous, thus very desirable for the hearing impaired who may be concerned with the social stigma and vanity associated with wearing a visible hearing aid. For example, in the aforementioned related '717 application, Shennib et al. describe an extended wear canal hearing device primarily positioned in the bony part of the ear canal. The canal device in the '717 application is of the air-conduction type since it relies on air-conducted sounds emitted by a receiver (speaker) to excite the eardrum. Similar to other air conduction hearing aids, acoustic sealing is required for the prevention of acoustic feedback.
In the other aforementioned '889 patent, the hearing device is similarly positioned inconspicuously in the bony part of the ear canal. However, the excitation of the eardrum occurs via a vibrational filament which makes direct contact thereto.
These and other hearing devices of the prior art rely on water-proofing elements integrated within for protection. For example, moisture guards are incorporated onto the microphone and the receiver for protecting the transducer from the damaging effects of moisture, cerumen and water-borne debris. The coating or enclosure of the body of the device must also be water proof since water exposure (e.g., during showering, or swimming) is expected for extended-wear devices that are worn continuously in the ear canal.
However, even with water proofing means incorporated onto the device, water and water-born debris is likely to accumulate on the body of the hearing device during its long term wear causing the device to ultimately malfunction. Furthermore, water contaminants in the ear canal may accumulate around the hearing device enhancing microbial growth which leads to irritation and infections in the ear canal.
Review of Protective Ear Covers
Ear canal protection for applications other than hearing device wear is well known. For example, Jordan-Ross in U.S. Pat. No. 4,916,758 discloses an ear protector for beautician use during applications of liquid treatments which may affect the ear canal. Adams in U.S. Pat. No. 5,488,961 discloses an ear plug that is hydrophobic for allowing hearing while preventing water from entering the ear canal during swimming and other water activities. The earplug is elongated with a lumen extending along the ear canal. These and other related inventions may interfere with a hearing device worn in the ear canal and inadvertently even damage the device or injure the device wearer, because they are merely intended to protect the ear canal.
A key goal of the present invention is to provide a hydrophobic barrier for the protection of a deep canal hearing device during its extended wear in the ear canal.
Another goal of the present invention is to protect the ear canal from water and water-borne contaminants during wear of a canal hearing device.